Variations of compression ratios

AI Thread Summary
Variations in compression ratios for diesel and Otto cycles are influenced by the ignition characteristics of the fuel; petrol engines require lower ratios to prevent pre-ignition, typically around 8:1 to 10:1, while diesel engines need higher ratios of about 20:1 to ensure ignition upon injection. The use of a charger can reduce the necessary compression ratio in diesel engines to approximately 16:1 by boosting air pressure. The discussion also raises the question of alternative engine cycles beyond Otto, diesel, or Seillinger, suggesting a curiosity about other technologies in automotive engineering. Understanding these compression ratios is crucial for optimizing engine performance and efficiency. Overall, the relationship between compression ratios and fuel types is essential for engine design.
mech-eng
Messages
825
Reaction score
13
Hi,all. What changes the variations of compression rations in diesel and otto cycles which are
always used in the engines. Are there any cycles used in automobile engines other than otto, diesel or seillinger?
 
Engineering news on Phys.org
In a petrol engine, the fuel must not ignite under compression until the spark occurs.
So compression ratio must be below about 10:1 for high octane and 8:1 for ULP.

Diesel fuel must ignite as it is injected so it needs about 20:1 compression to get high temperature.
If a charger is used to boost input air pressure then only about 16:1 will be needed to get same pressure.
 
  • Like
Likes 1 person

Thread 'Bubble formation in 4 mm gap vessel'

How did you find PF?: Via Google search Hi, I have a vessel I 3D printed to investigate single bubble rise. The vessel has a 4 mm gap separated by acrylic panels. This is essentially my viewing chamber where I can record the bubble motion. The vessel is open to atmosphere. The bubble generation mechanism is composed of a syringe pump and glass capillary tube (Internal Diameter of 0.45 mm). I connect a 1/4” air line hose from the syringe to the capillary The bubble is formed at the tip...
View full post »
Thread 'Calculate minimum RPM to self-balance a CMG on two legs'

Thread 'Calculate minimum RPM to self-balance a CMG on two legs'

Here is a photo of a rough drawing of my apparatus that I have built many times and works. I would like to have a formula to give me the RPM necessary for the gyroscope to balance itself on the two legs (screws). I asked Claude to give me a formula and it gave me the following: Let me calculate the required RPM foreffective stabilization. I'll use the principles of gyroscopicprecession and the moment of inertia. First, let's calculate the keyparameters: 1. Moment of inertia of...
View full post »
Thread 'Physics of Stretch: What pressure does a band apply on a cylinder?'

Thread 'Physics of Stretch: What pressure does a band apply on a cylinder?'

Scenario 1 (figure 1) A continuous loop of elastic material is stretched around two metal bars. The top bar is attached to a load cell that reads force. The lower bar can be moved downwards to stretch the elastic material. The lower bar is moved downwards until the two bars are 1190mm apart, stretching the elastic material. The bars are 5mm thick, so the total internal loop length is 1200mm (1190mm + 5mm + 5mm). At this level of stretch, the load cell reads 45N tensile force. Key numbers...
View full post »

Similar threads

Why are gas turbine engines not used in cars? Is what I think correct?
Replies
19
Views
2K
Expansion in non-adiabatic Otto / Diesel cycles
Replies
13
Views
2K
What Are the Advantages of a Rotating Detonation Engine for Naval Ships?
Replies
2
Views
3K
Direct Air Injection Engine Question
Replies
22
Views
2K
On-demand steam engine idea
Replies
14
Views
2K
Automotive Flash Point of Petrol & Diesel: Pressure & Self Ignition
Replies
16
Views
3K
Limiting factor in design of small gas turbine w/ LOW self sustain speed
Replies
5
Views
2K
Engineering Reviewing Efficiency of Otto & Diesel Cycle Heat Engines
Replies
8
Views
3K
How to estimate enthalpy change across a compressor in simple vapor compression cycle
Replies
1
Views
221
Wankel/rotary engine efficiency
Replies
7
Views
8K

Hot Threads

Recent Insights

Back
Top