Two-Stroke Engine Crankcase Fuel Injection and Intake Segmentation
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Solution Overview
Problem
Two-stroke engines face challenges in achieving high air mass flow rates while maintaining low exhaust emissions, particularly at low rotating speeds and under partial load, due to limitations in fuel supply and scavenging gas flow.
Innovation Solution
The design incorporates two intake channels: a first intake channel for air and a second intake channel for scavenging air, with a metering installation that supplies fuel directly to the crankcase interior, allowing for independent control of air and fuel flow to optimize air throughput and reduce exhaust emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fuel is supplied to the crankcase interior via the first intake channel, then fuel delivery is simplified, but air mass flow rate is limited and exhaust emissions increase
Solution Approach 1:
The patent divides the air supply system into two separate intake channels: a first intake channel for supplying air to the crankcase interior and a second intake channel for supplying scavenging air to the transfer channel. This segmentation allows independent optimization of each channel's flow characteristics, enabling high air mass flow rates while maintaining proper fuel delivery through the first channel.
Solution Approach 2:
The first intake channel serves dual functions: it supplies air to the crankcase interior for combustion and simultaneously delivers fuel to the combustion chamber. This multi-functionality simplifies the fuel supply system while maintaining efficient air flow through the dedicated second channel for scavenging.
2Productivity
If the second intake channel volume is increased to improve scavenging, then air throughput increases, but engine construction size increases
Solution Approach 1:
By segmenting the air supply into two separate channels with distinct functions, the patent optimizes the volume distribution. The second intake channel can be sized appropriately for scavenging requirements without unnecessarily increasing overall engine size, as the first channel handles the remaining air supply and fuel delivery functions.
Solution Approach 2:
The patent optimizes the volumetric parameters of the intake channels by adjusting the cross-sectional areas and lengths based on specific operating conditions. This allows maximizing air throughput through the second channel while keeping the overall engine compact by minimizing the first channel dimensions.
3Productivity
If fuel supply timing is delayed, then scavenging air delivery is improved, but fuel supply to combustion chamber becomes insufficient at low speeds
Solution Approach 1:
The patent segments the delivery timing of fuel and scavenging air through separate intake channels. The first intake channel delivers fuel with appropriate timing for reliable combustion at low speeds, while the second channel delivers scavenging air independently, preventing timing conflicts and ensuring both functions are optimized simultaneously.
4Device complexity
If a common throttle element controls both intake channels, then device complexity is reduced, but independent control of air and fuel flow is limited
Solution Approach 1:
The patent employs dynamic control strategies where the common throttle element can be selectively positioned to control different channels at different operating conditions. This dynamic adaptability allows independent control of air and fuel flow when needed, while maintaining simplified structure through the common throttle design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures sufficient fuel supply to the combustion chamber at low speeds and loads, reduces temporal delays in fuel delivery, and achieves low exhaust emissions by allowing for a larger volume of transfer channels and a smaller engine construction size.
Implementation Method 1
an injection valve for supplying fuel, the injection valve being configured to supply to the first flow path an entire quantity of fuel to be supplied to the two-stroke engine
Implementation Method 2
a piston configured to be guided in a reciprocating manner in the cylinder; the combustion chamber being delimited by the piston; a crankshaft rotatably mounted in the crankcase; the piston being configured to drive the crankshaft
Implementation Method 3
at least one transfer channel opening via a transfer window at the cylinder bore and opening into the crankcase interior via a passage opening; the at least one transfer channel being configured to establish a fluidic connection between the crankcase interior and the combustion chamber in a region of bottom dead center of the piston
Implementation Method 4
a common throttle element configured to control the first intake channel and the second intake channel; the common throttle element being pivotably mounted via a throttle shaft
Data Source
AI summary
A two-stroke engine includes a cylinder having a combustion chamber. The combustion chamber is delimited by a piston guided in a reciprocating manner in the cylinder and drives a crankshaft. A first intake channel opens into the crankcase interior. A transfer channel opens into the crankcase interior via a transfer window on a cylinder bore of the cylinder and via a passage opening. A second intake channel is provided for supplying scavenging air to the transfer channel. The first intake channel and the second intake channel are configured for supplying air. An injection valve configured for injecting the entire quantity of fuel to be supplied to the engine directly into the crankcase interior is disposed on the crankcase. A method for operating a two-stroke engine provides that the entire quantity of fuel to be supplied to the engine via a metering installation is supplied directly to the crankcase interior.