Can supercharging of an engine ever lead to reduced power?

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Discussion Overview

The discussion revolves around the effects of supercharging on the power output of a diesel engine operating on a dual air standard cycle. Participants explore the theoretical implications of increasing inlet temperature and pressure, and how these changes might affect various temperature and pressure points within the engine cycle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant observes that increasing inlet temperature and pressure leads to higher temperatures and pressures at certain points in the cycle (t2 and p2), but suggests that it may result in lower temperatures at t3 and t4, potentially reducing efficiency and power output.
  • Another participant questions the reasoning behind the decrease in t3 and t4 with increased pressure, seeking clarification on the relationship between these variables.
  • A participant references the constant volume process, suggesting that the ratio of t3 to t2 is linked to the ratio of p3 to p2, implying that an increase in p2 could lead to a decrease in t3.
  • Another contribution indicates that power output can decrease if there are issues with inlet geometry or insufficient injector size, leading to wasted energy in compressing air that cannot be effectively used for combustion.

Areas of Agreement / Disagreement

Participants express differing views on the effects of supercharging, with some supporting the idea that it can lead to reduced power output under certain conditions, while others seek clarification on the underlying mechanics and relationships between temperature and pressure variables.

Contextual Notes

The discussion includes assumptions about the relationships between temperature and pressure in the engine cycle, and the implications of inlet geometry and injector performance on overall power output. Specific mathematical relationships and definitions are not fully resolved.

chetanladha
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Hi,

I have decided to increase inlet T and P of a typical diesel engine (operatiing on dual air standard cycle).

THeoretically if all other parameters r same, I have observed that t2 (temp at the end of compression) and p2 increases, but t3 (temp at the end of constant volume heating) and t4 (temp at the end of constant pressure heating) tend to decrease because of increased p2.

This fall in temperatures result in reduced efficiency and power output.

Can any1 confirm if this is really true? As Practically, supercharging is supposed to boost the power o/p..

Thanks in advance
 
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Why would t3 and t4 decrease because of increased pressure?
 
constant volume process.

ratio of t3 to t2 = ratio of p3 to p2

p2 increases = t3 decreases

t4 is a function of t3..
 
Sorry i forgot 2 mention

THANKS FOR UR RESPONSE..
 
Yes output can decrease, if you have poor inlet geometry or injectors that arent big enough, you'll be spending power compressing air that you then can't use for combustion.
 

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