# Ideal Diesel Cycle Calculations

• moiznabi
In summary, the conversation discusses a 5-liter 10 cylinder, 4 stroke engine with a compression ratio of 18 and a cut-off ratio of 2.5, designed to produce 550kw at 12000rpm. The engine uses variable specific heats and air enters with a temperature of 280K and a pressure of 170Kpa after passing through a two-stage turbo charger and intercooler. The remaining parts of the problem involve finding the gas temperature after combustion, the approximate rate of consumption of diesel fuel, the air-fuel ratio, and the volumetric efficiency of the engine. To solve these parts, one must have the value for the 'heat or energy content' of the diesel fuel and use mass flow
moiznabi
Ideal Diesel Cycle Help??

## Homework Statement

A 5-liter 10 cylinder, 4 stroke engine to produce 550kw at 12000rpm. Compression ratio 18, cut-off ratio 2.5. Air enters with 280K and 170Kpa, after passing two-stage turbo charger and intercooler. Using variable specific heats.

(a) find gas temperature after combustion
(b) the approximate rate of consumption of diesel fuel
(c) the air-fuel ratio
(d) the volumetric efficiency of the engine.

## Homework Equations

LHV(diesel)=43.1 Mj/kg

## The Attempt at a Solution

I have solved part (a), what formulas do ii have to use for the rest of the parts.

One should have some value for the 'heat or energy content' (kJ/kg or Btu/lbm) of the diesel fuel in order to approximate the rate of consumption of diesel fuel.

Then with the mass flow rate of air and mass flow rate of fuel . . . .

What does one's textbook mention in regard to fuel energy content? Presumably there are examples of fuel consumption calculations.

I would suggest using the following equations for the remaining parts:

(b) The approximate rate of consumption of diesel fuel can be calculated using the formula:

Fuel consumption rate = Power output / (LHV of diesel * Volumetric efficiency * Air-fuel ratio)

(c) The air-fuel ratio can be calculated using the formula:

Air-fuel ratio = (1 / (Compression ratio * Cut-off ratio)) - 1

(d) The volumetric efficiency of the engine can be calculated using the formula:

Volumetric efficiency = (Actual air mass flow rate / Theoretical air mass flow rate) * 100

Where the actual air mass flow rate can be calculated using the formula:

Actual air mass flow rate = (Power output / (Specific fuel consumption * LHV of diesel))

And the theoretical air mass flow rate can be calculated using the formula:

Theoretical air mass flow rate = (Engine displacement * Engine speed * Air density)

I hope this helps in solving the remaining parts of the problem.

## 1. What is an ideal diesel cycle?

An ideal diesel cycle is a theoretical thermodynamic cycle that describes the operation of a diesel engine. It assumes that all processes are reversible, there are no heat losses, and the combustion process occurs at constant pressure.

## 2. What are the four processes involved in an ideal diesel cycle?

The four processes involved in an ideal diesel cycle are adiabatic compression, constant pressure combustion, adiabatic expansion, and constant volume heat rejection.

## 3. How does an ideal diesel cycle differ from an ideal Otto cycle?

An ideal diesel cycle differs from an ideal Otto cycle in that the combustion process occurs at constant pressure rather than constant volume. This results in a higher efficiency for the diesel cycle.

## 4. What is the efficiency of an ideal diesel cycle?

The efficiency of an ideal diesel cycle is given by the Carnot efficiency formula: efficiency = 1 - (1/r)^k, where r is the compression ratio and k is the ratio of specific heats for air.

## 5. What factors affect the efficiency of an ideal diesel cycle?

The efficiency of an ideal diesel cycle is affected by the compression ratio, the specific heat ratio of air, and the temperature at the beginning and end of the compression process. It is also affected by any heat losses that occur during the combustion and heat rejection processes.

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