Diesel Engine driving a generator

In summary, the diesel engine which drives a generator uses light fuel oil (LFO) with a calorific value of 19,600 BTU/lb. The generator has a current of 147.27 amps, and fuel consumption of 955.85 gallons per day.
  • #1
talaroue
303
0

Homework Statement



A diesel engine which drives a generator has an output of 60 hp operating at a n=31%. Then generator has a n=79% and supploes a load circuit at 240 V. The diesel engine uses light fuel oil (LFO) with a calorific value of 19,600 BTU/lb.
Calculate:
1. The generator output in kW
2. The current in the generator
3. the fuel consumption in gallons per day

(weight of LFO=8.3lb/gal; 1BTU=1055J)


Homework Equations


P=IV


The Attempt at a Solution


I am not sure if this is correct, its out of the book so I don't know.

For the first part i simple turned the 60hp into W knowing that 1 hp=745.7 W, so that gave me 44,742 W. I then multiplied that number by .79(the effecicency of the generator to get 35,346.2W which is equal to 35.35 kW. Is this correct?

For the second part I simpled used P=IV plugging in P=35.35kW, and V=240 to get 147.27 A. I believe this part is right aslong as the first part is right.

The third and final part i used what I learned in chemistry, stochiometry in a way,

35,346.2 W *(1 BTU/1055 W)*(1 lb/19,600 BTU)*(1 gal/8.3 lb)=2.06x10^-4 gals

everything except gals cancels, but the question asks gals/day but i don't know how I would do that...

Thanks for your help!
 
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  • #2
any ideas?
 
  • #3
I am just confusing myself more and more.
 
  • #4
Why can't I understand circuits :-/ thank god my major is Civil.
 
  • #5
talaroue said:

Homework Statement



A diesel engine which drives a generator has an output of 60 hp operating at a n=31%. Then generator has a n=79% and supploes a load circuit at 240 V. The diesel engine uses light fuel oil (LFO) with a calorific value of 19,600 BTU/lb.
Calculate:
1. The generator output in kW
2. The current in the generator
3. the fuel consumption in gallons per day

(weight of LFO=8.3lb/gal; 1BTU=1055J)


Homework Equations


P=IV


The Attempt at a Solution


I am not sure if this is correct, its out of the book so I don't know.

For the first part i simple turned the 60hp into W knowing that 1 hp=745.7 W, so that gave me 44,742 W. I then multiplied that number by .79(the effecicency of the generator to get 35,346.2W which is equal to 35.35 kW. Is this correct?

For the second part I simpled used P=IV plugging in P=35.35kW, and V=240 to get 147.27 A. I believe this part is right aslong as the first part is right.

The third and final part i used what I learned in chemistry, stochiometry in a way,

35,346.2 W *(1 BTU/1055 W)*(1 lb/19,600 BTU)*(1 gal/8.3 lb)=2.06x10^-4 gals

everything except gals cancels, but the question asks gals/day but i don't know how I would do that...

Thanks for your help!

In your equation: 35,346.2 W *(1 BTU/1055 W)*(1 lb/19,600 BTU)*(1 gal/8.3 lb)=2.06x10^-4 gals

Where did (1 BTU/1055 W) come from?
 
  • #6
Your diesel engine puts out 60 hp but it is only 31% efficient. Therefore the input energy to the engine is 193.5 hp. That is the energy the oil must supply to get 60 hp output.

1 hp=33475 btu/hr, 1 lb of oil provides 19,600 btu's, 1 gal of LFO weighs 8.3 lb, there are 24 hours in a day (assuming the engine 24 hours)

This information will give you gallons of LFO used per day
 
  • #7
RTW69: Where did you find that 1 hp=33475 btu/hr?

OmCheeto: I thought that it said 1 BTU/1055J but really it said 1 BTU=1055 J so I could just multiple change for BTU to J just by multipling. I think I am going to go with RTW69 said and see where that takes me.
 
  • #8
Were my other parts correct for this problem then?
 
  • #9
talaroue said:
RTW69: Where did you find that 1 hp=33475 btu/hr?

OmCheeto: I thought that it said 1 BTU/1055J but really it said 1 BTU=1055 J
It is the same thing in the context of your equation.
so I could just multiple change for BTU to J just by multipling.

Yes. But you converted 1 BTU = 1055 J to 1 BTU = 1055 W.
1 Joule does not equal 1 Watt.
I think I am going to go with RTW69 said and see where that takes me.
My conversion table says 1 hp = 42.4 btu/min, which does not yield 33475 btu/hr.
 
  • #10
I think I was wrong before can someone tell me if I am right now? (i am making another post right now)
 
  • #11
Part A: The generator output in kW

If the engine has a input of 193.55 hp that means the output of the generator has to be 193.55 correct? so then I just do 193.55*745.7 W/1000=144.33 kW?

Part B: The current in the gnerator load ciruit

If the generator has an output of 193.55 with a effeicency of 79% the input is 245 hp, so then I use P=VI solve for I=P/V I have 245 hp*745.7W/240 V=761.24 Amps

Part C: The fuel consumption

193.55hp*(33475BTU/hr)*(1 lb/ 19,600 BTU)* (1 gal/8.3 lb)*(24 hr/1 day)=955.85 gal/day
 
  • #12
or instead of the 193.55 hp should it be the input of the generator which is 245 hp?
 
  • #13
talaroue said:
Part A: The generator output in kW

If the engine has a input of 193.55 hp that means the output of the generator has to be 193.55 correct?

No. The initial problem stated:
A diesel engine which drives a generator has an output of 60 hp

ie. the output of the diesel engine is 60 hp.

The output of the generator will be less since it is only operating at 79% efficiency.
 
  • #14
1 Boiler horsepower (Bohp)=33,475 Btu/hr. It is a term used to rate boilers and is the energy needed to evaporate 34.5 lbs of water at 212 degrees F in one hour. You should probably use electric horsepower instead. I electric horsepower is 746 watts. 1 watt is 3.4129 Btu/hr or 1 electric horsepower is 2545 btu/hr. Sorry for the confusion.
 
  • #15
The output of the engine=the input of the generator? is this correct
 
  • #16
When I find the current in the generator load circuit do I use the power output? or input?
 
  • #17
talaroue said:
The output of the engine=the input of the generator? is this correct

Yes

talaroue said:
When I find the current in the generator load circuit do I use the power output? or input?

Output
 
  • #18
Ok, and why is that?
 
  • #19
talaroue said:
Ok, and why is that?

Why what? Yes or output?
 
  • #20
Why is it the output? Sorry about that
 
  • #21
talaroue said:
Why is it the output? Sorry about that

No. I am sorry. Your answers to parts 1 and 2 in your first post were correct. I guess I should have pointed that out.

Following my hints in posts #5 and #9, and RTW's first two sentences of post #6, will help solve part 3.
 

1. What is a diesel engine?

A diesel engine is a type of internal combustion engine that uses diesel fuel as its primary source of energy. It works by compressing air inside a cylinder, which then heats the air and ignites the fuel, resulting in combustion and the release of energy.

2. How does a diesel engine drive a generator?

A diesel engine is connected to a generator through a crankshaft, which converts the reciprocating motion of the pistons into rotational motion. This rotational motion is then transferred to the generator, which uses electromagnetic induction to convert it into electricity.

3. What are the advantages of using a diesel engine to drive a generator?

Some of the advantages of using a diesel engine for a generator include: high efficiency, low maintenance, and durability. Diesel engines are also more fuel-efficient than gasoline engines, making them a cost-effective option for powering generators.

4. How does a diesel engine differ from a gasoline engine?

The main difference between a diesel engine and a gasoline engine is the way they ignite fuel. Diesel engines use compression ignition, which means the air inside the cylinder is heated through compression and then the fuel is injected, causing combustion. Gasoline engines use spark ignition, where a spark plug ignites a mixture of fuel and air.

5. What are some common uses of diesel engine-driven generators?

Diesel engine-driven generators are commonly used in various industries and settings, such as: backup power for hospitals, data centers, and critical infrastructure, as well as for remote locations without access to a power grid. They are also used in construction, mining, and agriculture as a source of portable power.

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