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PRAKTIKUMMOTORBAKARKELOMPOKXX|1

LABORATORIUMMOTORBAKARFT-UB

SEMESTERGANJILTAHUNAKADEMIK2019/2020

BAB I PENDAHULUAN

1.1 Latar Belakang

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1.2 Tujuan Praktikum

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2|PRAKTIKUMMOTORBAKARKELOMPOKXX

LABORATORIUMMOTORBAKARFT-UBSEMESTERGANJILTAHUNAKADEMIK2019/2020

BAB II TINJAUAN PUSTAKA

2.1 Pengertian Motor Bakar

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2.2 Prinsip Kerja Motor Bakar Torak

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2.2.1 Prinsip Kerja Motor Bakar Torak Berdasarkan Langkah Kerja

2.2.1.1 Motor Bakar Torak 2 Langkah

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2.2.1.2 Motor Bakar Torak 4 Langkah

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2.2.2 Prinsip Kerja Motor Bakar Torak Berdasarkan Sistem Penyalaan

2.2.2.1 Motor Bakar Diesel (Compression Ignition Engine)

A. Pengertian

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B. Siklus Termodinamika

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C. Rasio Kompresi

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2.2.2.2 Motor Bakar Bensin (Spark Ignition Engine)

A. Pengertian

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B. Siklus Termodinamika

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C. Rasio Kompresi

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2.3 Karakteristik Bahan Bakar

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2.3.1 Flash Point

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2.3.2 Fire Point

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2.3.3 Auto-Ignition Point

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2.3.4 Viskositas

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2.3.5 Densitas

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2.3.6 Nilai Kalor

A. High Heating Value (HHV)

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B. Low Heating Value (LHV)

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2.3.7 Octane Number

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2.3.8 Cetane Number

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2.4 Karakteristik Kinerja Motor Bakar

2.4.1 Indikator Kinerja Motor Bakar

A. Torsi

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B. Daya Indikatif

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C. Daya Efektif

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D. Daya Mekanis

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E. Mean Effective Pressure

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F. Specific Fuel Consumption

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G. Efisiensi

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H. Air-Fuel Ratio dan Fuel-Air Ratio

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2.4.2 Indikator Operasional Motor Bakar

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A. Bukaan Katup (Throttle)

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B. Beban Mesin

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2.5 Hubungan Indikator Operasional terhadap Indikator Kinerja

2.5.1 Motor Bakar Diesel

2.5.1.1 Grafik Hubungan Putaran terhadap Torsi, Daya Efektif, dan SFC

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A. Grafik Hubungan Putaran terhadap Torsi

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B. Grafik Hubungan Putaran terhadap Daya Efektif

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C. Grafik Hubungan Putaran terhadap SFC

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2.5.1.2 Grafik Hubungan Putaran terhadap Daya Mekanis, Daya Indikatif,

dan MEP

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A. Grafik Hubungan Putaran terhadap Daya Mekanis

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B. Grafik Hubungan Putaran terhadap Daya Indikatif

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C. Grafik Hubungan Putaran terhadap MEP

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2.5.2 Motor Bakar Bensin

2.5.2.1 Grafik Hubungan Putaran terhadap Torsi, Daya Efektif, dan SFC

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A. Grafik Hubungan Putaran terhadap Torsi

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B. Grafik Hubungan Putaran terhadap Daya Efektif

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C. Grafik Hubungan Putaran terhadap SFC

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2.6 Governor Kecepatan

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2.6.1 Karakteristik Governor

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2.6.2 Tipe Governor

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2.7 Orsat Apparatus

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2.8 Diagram Sankey

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2.9 Teknologi Motor Bakar Terbaru

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2.9.1 Definisi

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2.9.2 Tujuan

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2.9.3 Prinsip Kerja

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2.9.4 Kelebihan dan Kekurangan

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2.9.5 Aplikasi dan Cara Perawatan

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BAB III METODE PENELITIAN

3.1 Waktu dan Tempat

Waktu :

Jam :

Tempat : Laboratorium Motor Bakar Teknik Mesin Universitas Brwaijaya

3.2 Pelaksanaan Praktikum

3.2.1 Instalasi Percobaaan Motor Diesel

Peralatan praktikum yang tersedia adalah instalasi percobaan (test rig)

lengkap, yang terdiri dari :

v Instalasi Percobaan Motor Diesel

v Unit Motor Diesel sebagai objek percobaan / penelitian.

v Instrumen pengukur berbagai variabel yang diperlukan (barometer,

higrometer, aeorometer, orsat apparatus).

v Peralatan bantu seperti instalasi air pendingin dan penyaluran gas buang.

Unit motor bakar yang digunakan adalah motor diesel dengan 4 silinder,

dengan spesifikasi sebagai berikut :

o Siklus : 4 langkah

o Jumlah silinder : 4

o Volume langkah torak total : 2164 cm3

o Diameter silinder : 83 mm

o Panjang langkah torak : 100 mm

o Perbandingan kompresi : 22 : 1

o Bahan bakar : Dexlite

o Pendingin : Air

o Daya Poros : 47 BHP / 3200 rpm

o Merk : Nissan, Tokyo Co.Ltd.

o Model : DWE – 47 – 50 – HS – AV

o Negara pembuat : Jepang




Gambar 3.1 Skema Instalasi Motor Diesel Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

3.2.2 Alat Ukur dan Fungsinya

Alat ukur serta fungsinya yang digunakan saat praktikum adalah sebagai

berikut :

a. Orsat apparatus

Digunakan untuk mengukur dan menganalisa gas buang (%).

Gambar 3.2 Orsat apparatus Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)



b. Barometer

Digunakan untuk mengukur tekanan atmosfer (mmHg).

Gambar 3.3 Barometer Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

c. Aerometer

Digunakan untuk mengukur massa jenis bahan bakar (kg/m3).

Gambar 3.4 Aerometer Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)




d. Flash Point

Digunakan untuk mengetahui titik nyala api suatu bahan bakar (oC).

Gambar 3.5 Flash Point Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

e. Diesel Engine Test Bed

Digunakan untuk mengetahui parameter-parameter yang menunjukkan

karakteristik motor bakar.

Gambar 3.6 Diesel Engine Test Bed Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)



f. Stopwatch

Digunakan untuk mengetahui waktu konsumsi bahan bakar (s)

Gambar 3.7 Stopwatch Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

g. Hygrometer

Digunakan untuk mengukur kelembaban relatif udara (%).

Gambar 3.8 Hygrometer Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)




h. Dynamometer

Digunakan untuk mengetahui gaya pembebanan pada poros (Kg).

Gambar 3.9 Dynamometer Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

i. Flowmeter air pendinginan

Digunakan untuk mengukur debit aliran air pendinginan (liter/jam).

Gambar 3.11 Flowmeter air pendinginan Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)



j. Flowmeter Bahan Bakar

Digunakan untuk mengukur konsumsi bahan bakar (ml).

Gambar 3.12 Flowmeter bahan bakar Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

k. Manometer

Digunakan untuk mengukur perbedaan tekanan dalam system (mmH2O).

Gambar 3.13 Manometer Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)




l. Viscometer

Digunakan untuk mengukur viskositas fluida (η).

Gambar 3.14 Viscometer Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

m. Bomb calorimeter

Digunakan untuk mengetahui kalor bahan bakar (Kcal/Kg)

Gambar 3.15 Bomb Calorimeter Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)



n. STARGAS 898

Digunakan untuk menganalisis kandungan gas buang.

Gambar 3.16 STARGAS 898 Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

3.3 Prosedur Pengambilan Data Praktikum

Setiap kelompok praktikum melaksanakan sendiri semua proses pengujian

dan pengambilan data yang diperlukan untuk memenuhi tujuan praktikum di atas.

Dalam melaksanakan proses pengujian tersebut, mahasiswa harus mengikuti

semua aturan dan tata tertib yang berlaku di laboratorium dan mengikuti semua

petunjuk asisten laboratorium yang bertugas.

Metode percobaan dengan variasi putaran, parameter yang diukur adalah :

1. Gaya Pengereman

2. Perbedaan Tekanan Masuk dan Keluar Nozzle

3. Kelembapan Udara

4. Suhu Gas Buang

5. Suhu Air Masuk dan Air keluar

6. Debit Bahan Bakar

7. Kandungan Gas Buang

8. Tekanan Udara

3.3.1 Prosedur Pengujian Motor Bakar

1. Persiapan Sebelum Mesin Beroperasi

a. Menyalakan pompa pengisi untuk mengisi air dalam tangki sampai level air

mencapai tinggi aman dan menyalakan cooling tower




b. Membuka kran air pada pipa-pipa yang mengalirkan air ke mesin dan ke

dinamometer.

c. Mengatur debit air yang mengalir pada flowmeter pada debit tertentu dengan

mengatur bukaan kran pada flowmeter.

d. Menekan switch power untuk menghidupkan alat-alat ukur.

e. Menghidupkan alarm air pendinginan yang akan memberitahu jika terjadi

overheating dan level air kurang.

f. Menyalakan dinamo power control dan atur kondisi poros mesin dalam

keadaan tanpa beban.

2. Cara Menghidupkan Mesin

a. Mengatur bukaan throttle sesuai yang diinginkan

b. Setelah semua persiapan di atas dipenuhi, menyalakan kunci kontak pada

posisi memanaskan mesin terlebih dahulu sampai indikator glow signal

menyala.

c. Memutar posisi kunci ke posisi START sambil mengurangi pembebanan

pada poros.

d. Setelah mesin menyala, biarkan mesin beroperasi beberapa saat untuk

menstabilkan kondisi mesin.

3. Cara Mengambil Data

a. Atur putaran mesin (rpm) dengan mengatur pembebanan pada dinamometer

sampai mendapatkan putaran yang diinginkan.

b. Tunggu kondisi mesin stabil kemudian lakukan pengambilan data yang

diperlukan.



3.3.2 Prosedur Penggunaan Orsat Apparatus

Gambar 3.17 Orsat Apparatus Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

Cara penggunaan Orsat Apparatus :

1. Set ketiga tabung I, II, III pada ketinggian tertentu dengan membuka keran A,

B, C dan mengatur tinggi larutan pada tabung I, II, III dengan menaik –

turunkan gelas B, kemudian tutup keran A, B, C setelah didapatkan tinggi

yang diinginkan. Posisi ini ditetapkan sebagai titik acuan.

2. Naikkan air yang ada pada tabung ukur C sampai ketinggian air mencapai 50

ml dengan cara membuka keran H dengan menaikkan gelas B. Setelah

didapatkan tinggi yang diinginkan, tutuplah kembali keran H.

3. Ambil gas buang dari saluran gas buang untuk diukur, salurkan melalui

selang yang dimasukkan ke dalam pipa H.

4. Buka keran H sehingga gas buang akan masuk dan mengakibatkan tinggi air

yang ada di tabung ukur C akan berkurang.

5. Setelah tinggi air pada tabung ukur turun sebanyak 50 ml (sampai perubahan

air mencapai angka 0) tutuplah keran H dan kita sudah memasukkan volume

gas buang sebanyak 50 ml.

6. Untuk mengukur kandungan CO2 buka keran A supaya gas buang bereaksi

dengan larutan yang ada pada tabung III dengan mengangkat dan

menurunkan gelas B sebanyak 5 – 7 kali.




7. Setelah 5 – 7 kali kembalikan posisi larutan III ke posisi acuan pada saat set

awal dan tutup keran C setelah didapatkan posisi yang diinginkan.

8. Baca kenaikan permukaan air yang ada pada tabung ukur C. Kenaikan

permukaan air merupakan volume CO2 yang ada pada 50 ml gas buang yang

kita ukur.

9. Untuk mengukur kandungan O2 dan CO ulangi langkah 6 dan langkah 7

untuk keran B dan keran A pada tabung II dan tabung I.

10. Baca kenaikan permukaan air pada tabung ukur C dengan acuan dari tinggi

permukaan air sebelumnya.

3.3.3 Prosedur Penggunaan STARGAS 898

Gambar 3.18 STARGAS 898 Sumber: Laboratorium Motor Bakar Jurusan Mesin Universitas Brawijaya (2019)

Cara Penggunaan STARGAS 898 :

1. Masukan gas probe pada pipa gas buang

2. Nyalakan STARGAS Gas Analyzer

3. Pilih fungsi MEASUREMENT pada halaman GAS ANALYSIS

4. Pilih fungsi STANDARD TEST pada halaman TEST SELECTION

5. Tekan MENU untuk menunjukkan FUNCTION BAR dalam halaman

measurement pada standard test

6. Print hasil analisis gas buang untuk percobaan pada putaran pertama.

7. Lepaskan gas probe dari pipa gas buang.

8. STARGAS Gas Analyzer berada pada kondisi Autozero

9. Ulangi dari langkah pertama untuk analisis gas pada percobaan kedua dan

selanjutnya.



3.3.4 Rumus Perhitungan

Adapun rumus – rumus yang digunakan dalam perhitungan hasil percobaan

adalah sebagai berikut :

1. Momen Torsi

lFT ×= (kg.m) (3-1)

Dimana :

T : Torsi (kg.m)

F : besar gaya putar (kg)

L : panjang lengan dinamometer = 0,358 (m)

2. Daya Efektif

2,716nTNe ×

= (PS) (3-2)

Dimana :

n : putaran (rpm)

Ne : daya efektif (PS)

T : momen torsi (kg.m)

3. Daya Efektif dalam kondisi standard JIS

NekNeo .= (PS) (3-3)

293273749 θ+

−=

PwPak ;

PsPw .ϕ=

Dimana :

Neo : daya efektif yang dikonfersi dalam JIS (PS)

k : faktor konversi


Pa : tekanan atmosfir pengukuran (mmHg)

Pw : tekanan uap parsial (mmHg)

θ : rata-rata temperatur ruangan saat pengujian (°C)

ϕ : kelembamam udara (%)

Ps : Tekanan udara standar pada temperatur θ (mmHg)




4. Mean Effective Pressure (MEP)

Pe = niVdzNeo

××

×× 45,0 ( kg/cm2 ) (3-4)

Dimana :

Pe : tekanan efektif

z : jumlah putaran poros engkol

n : putaran poros engkol (rpm)

i : langkah mesin

Vd : volume langkah (m3)

5. Fuel Consumption

10003600

××= ρtVFC (kg/jam) (3-5)

ρ dexlite = 0,836 gr/mL

Dimana :

𝐹𝐶 : Konsumsi bahan bakar (kg/jam)

𝑉 : Volume bahan bakar (ml)

𝜌 : Massa jenis bahan bakar (gr/ml)

T : Waktu konsumsi bahan bakar (s)

6. Panas Hasil Pembakaran

𝑄𝑏 = 𝐹𝐶 𝑥 𝐿𝐻𝑉 ( )Jamkcal

(3-6)

Dimana :

Qb : panas hasil pembakaran (kcal/jam)

FC : konsumsi bahan bakar (kg/jam)

LHV : Low Heating Value (kcal/kg)

7. Berat Jenis udara

( )woa

PsPaγϕ

θϕ

γγ .273273

760.. +

+×

−×=

(3-7)

Dimana :

Pa : Tekanan atmosfer pengukuran (mmHg)



Ps : Tekanan udara standard pada temperatur tertentu (mmHg)

ϕ : Relative Humidity / Kelembapan Relatif (%)

γo : Berat jenis udara kering pada 760 mmHg

θ : Temperatur bola kering(oC)

8. Koefisien Udara

1

21

PPP −

=ε (3-8)

Dimana :

PP −1 : beda tekanan pada nozzle (mmH2O)

1P : tekanan atmosfer saat pengujian (mmHg)

ε : koefisien udara

9. Massa alir udara melalui nozzle

( )21

2

..24... PPgdGs a −= γ

πεα (kg/s) (3-9)

Dimana :

Gs : Massa alir udara melalui nozzle (kg/s)

α : Koefisien kemiringan nozzle = 0,822

ɛ : Koefisien udara

d : diameter nozzle = 0,048 m

g : Gaya gravitasi = 9,81m/s2

aγ : Berat jenis udara (kg/m3)

𝑃1 – 𝑃2 : Perbedaan tekanan pada nozzle

10. Massa Alir gas buang

3600FCGsGg += (kg/s) (3-10)

Dimana :

Gg : massa alir gas buang (kg/s)

Gs : massa alir udara melalui nozzle (kg/s)





11. Panas yang terbawa gas buang

𝑄𝑒𝑔 = 𝐺𝑔.𝐶𝑝𝑔. 𝑇𝑒𝑔 − 𝑇𝑢𝑑 x 3600 (kcal/jam) (3-11)

Dimana :

Cpg : panas jenis gas buang (kcal/kg.oC)

Teg : suhu gas buang (°C)

Tud : temperatur(°C)

Gg : massa alir gas buang (kg/s)

Qeg : panas yang terbawa gas buang (kcal/jam)

12. Efisiensi kerugian dalam exhaust manifold ( gη )

%100xQbQeg

g =η (3-12)

Dimana :

gη : efisiensi kerugian (%)



13. Kerugian Panas Pendinginan (Qw)

Qw =ρ.Ww.Cpw (Two-Twi) (kcal/jam) (3-13)

Dimana :

ρ : Massa jenis air = 1 kg/liter

Ww : debit air pendinginan (liter/jam)

Cpw : panas jenis air = 1 kcal/kg.oC

Two : temperatur air keluar (oC)

Twi : temperatur air masuk (oC)



14. Efisiensi Kerugian Panas dalam cooling water( wη )

%100xQbQw

w =η (3-14)

Dimana :

wη : efisiensi kerugian panas (%)

Qw : kerugian panas pendinginan (kcal/jam)


15. Efisiensi Thermal Efektif ( eη )

%100632××=QbNe

eη (3-15)

Dimana :

eη : efisiensi efektif (%)



16. Efisiensi Mekanis ( fη )

( )ewgf ηηηη ++−= %100 (3-16)

Dimana :

fη : efisiensi gesekan (%)

gη : efisiensi kerugian gas buang (%)

wη : efisiensi kerugian air pendinginan (%)

eη : efisiensi efektif (%)

17. Ekuivalen daya terhadap konsumsi bahan bakar (Qf )

𝑄𝑓 = !"#.!"!"#

(PS) (3-17)




Dimana :

LHV : Low Heating Value (kcal/kg)


18. Daya Mekanis

%100xQf

Nf fη= (3-18)

Dimana :

Nf : daya mekanis (PS)

fη : efisiensi gesekan (%)

Qf : kerugian karena gesekan (PS)

19. Daya Indikasi NmNeNi += (PS) (3-19)

Dimana :

Ni : daya indikasi (PS)


Nm : daya mekanis (PS)

20. Specific Fuel Consumption Effective

NeFCSFCe =

(3-20)

Dimana :

SFCe : Specific Fuel Consumption Effective



21. Specific Fuel Consumption Indicated

NiFCSFCi =

(3-21)

Dimana :

SFCi : Specific Fuel Consumption Indicated




Ni : daya indikatif (PS)

22. Panas Hasil Pembakaran yang diubah menjadi Daya Efektif

NeQe .632= (3-22)

Dimana :

Qe : panas efektif (kcal/jam)


23. Panas yang hilang karena sebab lain

𝑄𝑝𝑝 = 𝑄𝑏 − 𝑄𝑒𝑔 − 𝑄𝑤 − 𝑄𝑒 (3-23)

Dimana :

Qpp : panas yang hilang karena sebab lain (kcal/jam)



Qw : kerugian panas pendinginan (kcal/jam)

Qe : panas efektif (kcal/jam)

24. Efisiensi Thermal Indikasi

%100632××=QbNi

iη (3-24)

Dimana :

iη : efisiensi indikasi (%)

Ni : daya indikasi (PS)


25. Efisiensi Mekanis

%100xNiNe

m =η (3-25)

Dimana :

mη : efisiensi mekanis (%)




Ni : daya indikasif (PS)


26. Efisiensi Volumetrik

%100...60.. xiVdn

zGs

av γ

η = (3-26)

Dimana :

vη : efisiensi volumetric (%)

z : jumlah poros engkol

Vd : volume engkol (m3)

I : langkah mesin

Gs : massa alir udara melalui nozzle (kg/s)

n : putaran poros (rpm)

𝛾a : Berat jenis udara (kg/m3)

27. Perbandingan Udara dan Bahan Bakar

3600xFCGsR =

(3-27)

Dimana :

R : rasio udara bahan bakar

Gs : aliran udara melalui nozzle (kg/s)


28. Rasio Udara Bahan Bakar Teoritis

22222223,12 116,671,113,12)76,3(85,17 NOHCONOHC ++→++ (3-28)

HMCM

NMOMFARo s

βα

βα

βα

+

⎟⎠

⎞⎜⎝

⎛ ++⎟⎠

⎞⎜⎝

⎛ +=

22 476,3

4)/(

Dimana :

Ro : Rasio udara bahan bakar teoritis

2OM : Massa relatif oksigen



2NM : Massa relatif nitrogen

CM : Massa relatif karbon

HM : Massa relatif hidrogen

29. Faktor Kelebihan Udara

RoR

=λ (3-29)

Dimana : λ : faktor kelebihan udara

R : rasio udara bahan bakar

Ro : rasio udara dalam bahan bakar teoritis

30. Faktor Koreksi Standard 5,0

⎥⎦

⎤⎢⎣

⎡=

st

st

TT

PP

A = 5,0

273273

⎥⎦

⎤⎢⎣

⎡

+

+

st

st

TT

PP

(3-30)

Dimana :

A : faktor koreksi

Pst : tekanan atmosfer = 760 mmHg

Tst : 25 ˚C

P : tekanan udara atsmosfer (mmHg)

T : temperatur ruangan (oC)

31. Daya Efektif Standard

( ) NeANe st .= (3-31)

Dimana :

( )stNe : daya efektif standar (PS)

A : faktor koreksi





32. Torsi Efektif Standard

( ) TAT st .= (3-32)

Dimana :

( )stT : torsi efektif standar (kg.m)

A : faktor koreksi

T : torsi (kg.m)

33. Pemakaian Bahan Bakar Efektif Standard

( )A

SFCeSFCe st = (3-33)

Dimana :

SFCest : Pemakaian Bahan Bakar Efektif Standar

SFCe : Specific Fuel Consumption Effective

A : faktor koreksi

34. Analisa Gas Buang

bab i pendahuluan -...

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