Define Related Product Limit in Products Detail Page

/*
 * Related Products Limit
 */

function woo_related_products_limit() {
    global $product;

    $args['posts_per_page'] = 3;
    return $args;
}

add_filter('woocommerce_output_related_products_args', 'jk_related_products_args');

function jk_related_products_args($args) {
    $args['posts_per_page'] = 3; // 4 related products
    $args['columns'] = 1; // arranged in 2 columns
    return $args;
}